Introduction:

The accuracy of fractional flow reserve (FFR) and quantitative flow ratio (QFR) in assessing coronary artery disease in severe aortic stenosis (AS) patients may be affected by the severity of AS.

Aim:

We investigated the relationship between aortic valve area (AVA) and the diagnostic performance of QFR in this context.

Material and methods:

We analyzed 416 intermediate coronary lesions in 221 severe AS patients using FFR and QFR, categorizing them based on AVA into two groups: AVA < 0.5 cm² and AVA ≥ 0.5 cm².

Results:

In all, 47 (21.2%) patients had an AVA < 0.5 cm². The median FFR and QFR values were comparable between groups, with a high agreement rate: interclass coefficient of 0.96 (95% CI: 0.94 to 0.97) for AVA < 0.5 cm² and 0.97 (95% CI: 0.97 to 0.98) for AVA ≥ 0.5 cm². Concordance in detecting significant ischemia was 96.3% for AVA ≥ 0.5 cm² but dropped to 86.5% for AVA < 0.5 cm², with discrepancies mainly in cases where FFR was negative and QFR positive. Multivariable analysis showed AVA and %DS as independent predictors of discordance; AVA ≥ 0.5 cm² had an OR of 0.229 (95% CI: 0.095 to 0.548; p < 0.001), and each 1% increase in %DS increased the odds by 1.070 (95% CI: 1.034 to 1.107; p < 0.001).

Conclusions:

In severe AS, QFR closely correlates with FFR. However, patients with AVA < 0.5 cm² might exhibit a higher incidence of false-positive ischemia detection by QFR.